1. Field of the Invention
This invention relates to the construction industry and in particular to an improved method and apparatus for trying metal rods such as rebar together. The method and apparatus of the invention are particularly suited to blind tying reinforcing rods in a concrete masonry unit wall structure.
2. Description of the Prior Art
In the construction industry, it is often necessary no tie together two or more rods such as rebar used for reinforcing a structure. As an example, in the construction of walls for homes and businesses, concrete masonry units (CMUs) or fired clay masonry units (FCMUs) are stacked and reinforced with rebar. In a typical wall construction, a foundation or stem wall is first poured in place. The foundation includes evenly spaced steel reinforcing rods that are anchored in the foundation. The reinforcing rods are typically formed of a length of rebar embedded in the foundation. The reinforcing rods extend vertically upward from the foundation by distance of about two to three feet.
During the construction process, rows of concrete masonry units are stacked on the foundation with mortar placed between the units. The concrete masonry units are usually rectangular in shape and have two openings or cells formed through the unit. After the wall has been erected, the cells of the concrete masonry units can be filled with concrete grout to rigidify the structure.
With such a wall constructed of concrete masonry units, the first couple of rows of masonry units are placed over the steel reinforcing rods anchored in the foundation. In order to provide maximum strength for the wall, however, it is desirable to extend the reinforcing rods so that each row masonry units is reinforced. Typically, this is accomplished by tying or splicing additional lengths of reinforcing rods, such as metal rebar, to the reinforcing rods anchored in the foundation.
A problem associated with this method of construction is in tying the additional lengths of rebar to the reinforcing rods anchored in the foundation. Since the reinforcement rods are contained within the concrete masonry units, this is a "blind tie". One method of tying the rods together, is to build the wall to its final height and then insert the additional lengths of rebar through the completed wall. Access holes are then knocked through the concrete masonry units at the places where the pairs of rods come together. This enables the rods to be tied together using wire. Sometimes the access holes are cut in the concrete masonry units before their placement in the wall. The access holes must necessarily be repaired following completion of the wall. As is apparent, this is an expensive and time consuming process. In addition, the holes may detract from the overall appearance of the finished wall, especially with decorative or tinted masonry units.
A second method for tying the reinforcing rods is to the rods together before the wall is constructed, and then to erect the wall over the tied reinforcing rods. From the standpoint of safety, however, this is a very undesirable procedure. This is because the full height of the tied reinforcement rods may be eight feet or more. The masons constructing the wall, must therefore lift each concrete masonry unit this entire height in order to place the masonry units over the tied reinforcement bars. Since these concrete masonry units typically weigh on the order of 40 pounds or more, back injuries are common. Even more dangerous is that a mason will sometimes stand on a stool, or another masonry unit stood on its end, to gain an additional height advantage for lifting the masonry unit. This increases the possibility of a man falling and injuring himself. This problem is compounded because the masons often work on scaffolds which are many feet above the ground.
In view of the foregoing, there is a need in the art for improved procedures for tying reinforcing rods and other elongated members. Accordingly, it is an object of the present invention to provide an improved method and apparatus for tying or splicing elongated members, such as metal reinforcement rods made of rebar. It is a further object of the present invention to provide an improved method and apparatus for blind tying reinforcement rods in a concrete masonry unit wall structure. It is yet another object of the present invention to provide an improved method and apparatus for tying reinforcement rods and other elongated members that is fast, efficient and inexpensive and which permits concrete masonry unit walls to be safely constructed.